#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
#define rep(i, a, b) for (int i = (a); i <= (b); i++)
#define per(i, a, b) for (int i = (a); i >= (b); i--)
#define endl '\n'
const int N = 3e4 + 5;

int n, m;
int a[N];

int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  cin >> m >> n;
  rep(i, 1, n) cin >> a[i];
  sort(a + 1, a + n + 1);
  int r = n, l = 1, cnt = 0;
  while (l < r) {
    if (a[l] + a[r] <= m)
      r--, l++;
    else
      r--;
    cnt++;
  }
  if (l == r) cnt++;
  cout << cnt;
  return 0;
}